21389721453 has 18 divisors (see below), whose sum is σ = 32820603114. Its totient is φ = 13421000064.

The previous prime is 21389721449. The next prime is 21389721499. The reversal of 21389721453 is 35412798312.

It is a happy number.

21389721453 is a `hidden beast` number, since 2 + 1 + 389 + 7 + 214 + 53 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 14089215204 + 7300506249 = 118698^2 + 85443^2 .

It is not a de Polignac number, because 21389721453 - 2² = 21389721449 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21389721399 and 21389721408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21389721653) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 4109226 + ... + 4114427.

Almost surely, 2^21389721453 is an apocalyptic number.

It is an amenable number.

21389721453 is a deficient number, since it is larger than the sum of its proper divisors (11430881661).

21389721453 is a wasteful number, since it uses less digits than its factorization.

21389721453 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8223693 (or 8223673 counting only the distinct ones).

The product of its digits is 362880, while the sum is 45.

The spelling of 21389721453 in words is "twenty-one billion, three hundred eighty-nine million, seven hundred twenty-one thousand, four hundred fifty-three".